The Heat Source Mechanism Of Wumishan Strata Geothermal Resources In Xiong’an New Area,North China

Xiong’an new area has rich geothermal resources,and heat source research plays an important role in the geothermal system.The research in this paper is mainly aimed at analyzing geothermal characteristic parameters such as the distribution of current heat flow,the distribution and residual heat influence of igneous rocks,and lithosphere thermal structure in the study area,forming an understanding of the cause of its heat source.The sample heat production test results show that the heat production of the sedimentary rocks in Xiong’an new area is lower than 1.60μW/m~3,and the average heat productions of igneous and metamorphic rocks are 1.06μW/m~3 and 0.53μW/m~3,the thermal conductivity of the sample is between 1.49W/(m·K)and 6.69W/(m·K).The sedimentary layer contributes 5.19m W/m~2 to 9.66m W/m~2 to the surface heat flow.Rongcheng and Niutuozhen Salients developed beaded medium-acid intrusive rocks during the Yanshanian period.Based on the simulation results of the finite element method,the thermal equilibrium with the surrounding rock is reached after 0.5Ma,and the difference in thermal physical properties between the igneous rocks and the surrounding rocks after cooling makes the local heat flow approximately 3.55m W/m~2higher.The Langgu Sag and Baxian Sag developed basal intrusive rocks in the Paleogene,reached thermal equilibrium with the surrounding rocks through 0.2Ma,and had little effect on the current heat flow after cooling.The temperature of Moho surface in Xiong’an new area is between 500℃and 600℃,which is higher in the southwest than in the northeast.The deeper ground temperature is affected by the stretching and thinning of the North China Craton.High values are concentrated on the east side of the study area,and low values are concentrated on the northwest side of the study area.The three structural regions divided in the study area are all“cold crust and hot mantle”type thermal structures.The thickness of the hot lithosphere is 102km to 122km.The mantle heat flow from west to east is 30m W/m~2,34m W/m~2,and 35m W/m~2,contributed 53%to 62%of the heat flow,the crust produced 26.3m W/m~2,26.1m W/m~2,and 21m W/m~2,and contributed38%to 47%of the heat flow.The Yanshanian intruder provides more than 3.55m W/m~2of approximately 6%heat flow to the central salients.Under the influence of groundwater convection,the measured heat flow value becomes lower in the groundwater replenishment area at the front of the mountain,and becomes higher in the raised area where the deep fault develops.The thermal conduction of crust-mantle heat flow and thermal convection caused by deep faults together constitute the current geothermal state of Xiong’an new area.